Income and Expenses Relating to Life Insurance Operations - Life Insurance Premiums and Related Investment Income (Parenthetical) (Detail) - JPY (¥) ¥ in Millions |
6 Months Ended | |
|---|---|---|
Sep. 30, 2026 |
Sep. 30, 2025 |
|
| Net Investment Income [Line Items] | ||
| Trading Securities, Unrealized Holding Gain (Loss) | ¥ 100,176 | ¥ 64,149 |
| Life insurance related investment income loss | ||
| Net Investment Income [Line Items] | ||
| Trading Securities, Unrealized Holding Gain (Loss) | ¥ 25,692 | ¥ 30,360 |